Volume 18 Issue 1

Compression alfalfa into briquettes is an effective way to solve the problem of storage and transportation. In the process of compression, heat is generated, which raises the temperature in the material. The appropriate temperature can improve the quality of alfalfa briquettes. In this paper, the effect of assisted vibration frequency, moisture content, and particle size on the compression temperature were tested. The results showed that when the vibration was applied, the material particle temperature in the mold rose significantly, and the core particle temperature rose faster than the edge temperature. The vibration frequency was the most significant factor affecting heat transfer in the three studied factors. When the moisture content and particle size were constant, the heat transfer effect increased first and then decreased with the vibration frequency, and it had an optimal value at 17 Hz. When the vibration frequency and particle size were constant, the heat transfer effect increased first and then decreased with the moisture content. It had an optimal value of 20%. The experimental results explained the effect of vibration frequency, moisture content, and particle size on temperature variation during alfalfa compression and provided a basis for reasonable process parameters.

The effects of pre-impregnation on surface roughness, wettability, and morphological structure of densified aspen and fir wood were investigated.
Wood specimens were impregnated with paraffin, linseed oil, and styrene after pre-vacuum treatment. The impregnated specimens were densified using compression ratios of 20% and 40% at 120 °C, 150 °C, and 180 °C. The roughness decreased and the contact angle increased in all impregnated specimens (undensified and densified). Compared to paraffin and linseed oil-impregnated specimens, lower roughness and higher contact angle were found in styrene-impregnated specimens. After densification, the roughness and wettability of the wood specimens decreased. More successful results (lower roughness and higher contact angle) were generally obtained in specimens densified with high compression ratio (40%). In both untreated and impregnated specimens, the contact angle increased with increasing compression temperature. While the effect of compression temperature on the roughness of the fir specimens was not significant, the roughness of the aspen specimens (especially styrene-impregnated) decreased with the increase in temperature. Scanning electron microscopy observations indicated that impregnation agents (especially styrene) clung to wood cell walls and partially or completely filled the lumens. This was positively correlated with the determined roughness and wettability. Pre-impregnation facilitated wood densification without significant cell deformations.

Three kinds of cellulose nanocrystals (CNCs) were added into waterborne polyurethane (WPU) and nanocomposite films that were prepared by solution casting. The influence of different ionic function groups on microstructure and properties of composite films was investigated. Compared with sulfated CNCs (SCNCs) and TEMPO oxidized CNCs (TOCNCs), FE-SEM images showed that cationized CNCs (CaCNCs) had better dispersion in composite films. The thermal decomposition of these composite films was delayed by 15 °C compared with pure WPU film. The tensile strength and fracture work of CaCNC/WPU composite film increased by 11.9% and 8.4%, respectively. The light transmittance of CaCNC/WPU composite film was highest among the 3 composite films, but its oxygen permeability was the lowest. In sum, the composite film with CaCNCs had optimal strength, toughness, light transmittance, and oxygen barrier properties, which is consistent with good compatibility of the two components and densest structure observed in SEM. There may be an ionic attraction and hydrogen bonds of CaCNCs and WPU in the composite film. The composite films are expected to have applications in food packaging, furniture coatings, and biomedical fields.

The development and utilization of biomass energy based on the thermochemical conversion of crop biomass to produce hydrogen are of great significance for promoting China’s ecological civilization construction, energy revolution, and low-carbon economic development. Henan province is one of the largest agricultural and pasturage provinces in China. Based on the analysis of the status and trends of Henan’s biomass energy (BE) development, this paper summarizes the present status of the construction of ecological civilization (CEC) and the factors restricting its development.  Challenges in developing biomass energy are analyzed systematically, and strategies and key technical directions for future biomass energy development are discussed. Finally, the paper presents countermeasures and suggestions for CEC based on the development of BE, which will vigorously promote the development and utilization of BE and the process of CEC. This research provides a reference for the further development of BE and CEC in the future.

Improving the detection accuracy of hyperbola in B-scan images has been a considerable challenge for ground penetrating radar (GPR) to detect tree roots. In this paper, a method for data enhancement and target detection, both based on deep learning was proposed to identify hyperbolas in GPR B-scan images. First, the authors used a cyclic consistent adversarial network (CycleGAN) to augment the original data. In this procedure, the hyperbolic features of the images were preserved and created a wider variety of training samples. Then, the authors could apply the enhanced dataset to the YOLOv5 detection model to evaluate the effectiveness of their method. Meanwhile, the detection effects of Yolov3, Yolov5, Faster R-CNN, and CenterNet detection models on the enhanced dataset were compared. The results showed that applying the enhanced dataset to the Yolov5 detection model exhibited better detection accuracy compared to other combinations of datasets and detection models. The authors demonstrate that the proposed method increases data diversity and the number of samples, improving the precision and recall of hyperbolic curves. These results provide a new method for tree root localization with important effects.

Wet spinning was studied for lignocellulose nanofibrils (TOLCNF) obtained by TEMPO oxidation and mechanical defibrillation of deep eutectic-like solvent-treated lignocellulose. First, the morphological characteristics, water retention value, and specific surface area of the TOLCNF were studied. The effects of the TOLCNF concentration (1.5, 2.0, and 2.5 wt%) and spinning rate (0.1, 1.0, and 10 mL/min) on the wet-spun filament diameter, orientation index, and tensile properties were studied. With an increase in the TOLCNF concentration, the average diameter increased, whereas the orientation index and tensile strength decreased. An increased spinning rate resulted in an increased orientation index and tensile strength but a decrease in the average diameter. To further extend their applicability, Ag nanoparticles (AgNPs) were grown in situ on the filament surface using UV irradiation. Spherical AgNPs with diameters of 30 to 90 nm were observed using scanning electron microscopy. An increased AgNP content improved the tensile strength and elastic modulus of the filaments.

In order to determine the influence of bast fibers isolated from Wikstroemia bark on the durability of paper, self-made paper was prepared using bagasse pulp mixed with Wikstroemia bark pulp using Kaihua paper manufacturing technology. The durability properties of the paper obtained with different proportions of Wikstroemia bark pulp were measured and analyzed. The results showed that Wikstroemia bark can lower the acidity, improve the mechanical strength, and delay the aging of paper. The mechanical strength showed an exponential relationship with the amount of Wikstroemia bark pulp added to the paper pulp. There was a linear positive correlation between the initial polymerization degree of the paper and the amount of Wikstroemia bark pulp, while the molecular fracture rate of the paper with Wikstroemia bark pulp was considerably reduced. Wikstroemia bark fibers are long fibers with high strength. At the same time, Wikstroemia bark fibers differ greatly in length, so the uniformity can meet the requirements. The durability of the paper made from only bagasse pulp was poor, but the overall strength and polymerization degree of the paper improve after being mixed with Wikstroemia bark pulp.

This work studied the effect of the dewatering conditions on the behavior of fiber foams during dewatering and on the final structure of the formed, thick, lightweight lignocellulosic materials. The vacuum level, fiber type, consistency, and basis weight of the fiber foam were all varied. During dewatering, the time evolution of the thickness of the fiber foam in the mold was studied, and the dryness of the fiber foam immediately after dewatering was measured. The density and pore size profiles of the final dry materials was measured using X-ray microtomography (µCT).

To elucidate chemical linkages between lignin and polysaccharides, the aqueous mixed solutions of coniferin-[α-13C], syringin-[α-13C], D-glucose-[6-2H], and phenylalanine ammonia-lyase inhibitor were injected into a living wheat stalk. Internode tissues with high abundance of 2H-13C were collected. The milled wood lignin, lignin-carbohydrate complex (LCC), and residual LCC (R-LCC) with enrichment of 2H-13C were isolated. The 13C and 2H abundances showed that the lignin and polysaccharides of internode tissues were labeled by 13C and 2H, respectively. Analysis with carbon-13 nuclear magnetic resonance (13C-NMR) showed that ketal and benzyl ether bonds were formed between α-C of lignin and carbohydrates. The R-LCC and LCC were further treated with enzymes to obtain enzymatic degraded R-LCC (ED-R-LCC) and enzymatic degraded LCC (ED-LCC). 13C-NMR spectra of ED-LCC showed that the α-C of lignin side chain was combined with 6-C of carbohydrates by ether, ester, and ketal linkages. 1H-NMR differential spectra of ED-LCCs revealed an LC linkage of benzyl ether bond. Glucan-lignin (En-R-GL) and xylan-lignin (En-R-XL) complexes were separated from ED-R-LCC by ionic liquid. A part of lignin α-C was linked to cellulose 6-C by benzyl ether and α-ketal linkages. 13C-NMR spectra of En-R-XL showed there were α-benzyl ether and α-ketal bonds between lignin and xylan.

Laccase activity secreted by Pleurotus eryngii Han 1787 and Lentinus edodes Han 1788 grown on six types of agroindustrial wastes was investigated. Maximum laccase activity of P. eryngii Han 1787 on Ulmus pumila, Juniperus formosana, Pinus tabuliformis, cottonseed shell, corncob, and leaf of corncob was nearly 5.77-fold, 2.37-fold, 2.78-fold, 2.81-fold, 11.53-fold, and 6.73-fold higher than that of L. edodes Han1788 on corresponding agroindustrial wastes. In general, the capacity of secreting laccase of P. eryngii Han 1787 was superior to that of L. edodes Han 1788. Furthermore, laccase activity of P. eryngii Han 1787 on the leaf of corncob, the corncob, Ulmus pumila, and Juniperus formosana was relatively stable during the whole fermentation process. Different fungi showed different preferences in different agroindustrial wastes to secret laccase on whole fermentation stage. The presence of leaf of corncob was useful for improving laccase activity of P. eryngii Han 1787, while L. edodes Han 1788 was more preferred to produce laccase along with the presence of Juniperus formosana. These results were preliminary conducive in laying the foundation for increasing industrial laccase-producing strains and producing low-cost laccase.